Corrosion preventing compositions and process



United States Patent CORROSION PREVENTING COMPOSITIONS AND PROCESS Hermann Gysling, Basel, Switzerland, assignor to J. R. Geigy A.-G., Basel, Switzerland, a Swiss firm No Drawing. Application August 22, 1955 Serial No. 529,913

Claims priority, application Switzerland September 16, 1954 15 Claims. (Cl. 252-137) The present invention concerns a process for the protection of copper and copper alloys with base metals against corrosion when in contact with water or aqueous' alkaline solutions. It also concerns agents, in particular cleansing agents, the aqueous or aqueousaalkaline solutions of which, due to a content of the protective agents against corrosion usable according to the present invention, have no or only an inconsiderable corrosive action on scoured surfaces of copper and alloys thereof with base metals.

It has been found that scoured surfaces of copper andlalloys of copper and base. metals; can be protected' against corrosion in contact with water and. imparticular with: aqueous alkaline'solutions if slight amounts of:- such 2-guanidino-aryloimidazole1' compounds? containing. no watersolubilising, groups which dissociate. acid. in neutral water and which are at least very slightly soluble in..water or in aqueous solutions, are added tothe water or, to. the solutions.

2-guanidino-aryloimidazole. compounds used according to the present invention can contain as aryl radicals,v for. example, thebenzeneor the naphthalene ring whichcan, be further substituted, for example with halogen,. alkyl, alkoxy, nitro, acylamino, alkylsulphonyl, arylsul phonyl or sulphonic acid amide groups. They may not contain, however, any groups either as such or in the form of their watersolubilising salts which dissociate acid in neutral water such, as, for example, carboxyl, sulphonic acidor phosphonic acidgroups. As they. must. be, water soluble, even if only slightly so, the benzimidazolevcomp ounds are to be preferredito those-withliiglier condensed rings. For example,v 2-guanidinorbenzimidae zole, 2 guanidino-6-chloro-., -6-methyl=,. -6.-methoxyor -6-ethoxy-benzimidazole, 2-guanidino-4- or. -6=nitro-benz= imidazole, 2-guanidino-4- or, -6racetylamino-benzimidazole, 2-.guanidino-6-methylsulphonyl-, -ethylsulphonyl:, or. -nbuty1sulphonybbenzimidazole, Z-guanidiho-henzimidazole 6-sulphonic acid dimethylamide,. -diethylamide,. -piperidide ,or -morpholide, Z-guanidino- LS:1.2Gnaphthimidazole can be used. Because of itseasy accessibility andfavourable water solubility, 2-guanidino-benzimidazole isto bepreferred to all other, compounds.

Some of, the Z-guanidino-aryloimidazole compounds useableaccording to the present invention, are knownbut. all canbe produced easily according to known methods. from aromatic o-diamiuocompounds bycondensation, with dicyanodiamide in acid solution.

Very small amounts of these.2 guanidino-arylo-imidazole compounds, for example 01 to 100mg. per litre; protect scoured copper and alloys thereof with base metals such as, e.g. brass. or nickel silver,xfrom corrosive action when in contact with water-or aqueous alkaline solutions, in particular in a pH range of from 8 to 12. The aqueous alkaline solutions can contain forexample: lithium, sodium or potassium salts ofcarbonic acid'or' the-oxyacids of boron,- silicium or phosphorus hHViflgB basic reaction. They may also contain neutralisalts' suchas sodium sulphate, sodium chloride, potassium sulphate or potassium chloride etc. such-as are the usual additives to capillary active cleansing agents as well as capillary active wetting, dispersing and cleansing agents which contain lipophilic hydrocarbon radicals and hydrophilici groups. Examples of such capillary active agents afei the fatty alcohol polyglycol ethers, the alkyl phenol poly glycol ethers, the fatty acid alkanol amides and polyglycol ethers thereof, the alkali and ammonium salts ofthe sulphuric acid half esters offatty alcohols, of the sulphated mono-fatty acid esters of polyalcohols, the alkali and ammonium salts of alkyl and alkylaryl s'ul' phonic acids; of sulph'osuccinic' acid esters" and of fatty? acids which contain lipophilic radicals.

Particularly in aqueous-alkaline solutions of wetting. dispersing and cleansing agents which contain the usual; alkali salts of polyphosphoric acids which make calciumions unharmful, such as e.g. tetrasodium pyrophospha'te',i' pentasodium triphosphate, sodium hexametaphosphate' or mixtures of the alkali saltsof such polyphosphoric acids; the 2-guanidino-arylo-imidazole compounds used accord ing to the present invention protect scoured copper and alloys thereof with base metals from corrosion when in contact with these solutions. They also protectco'pper from attack by aqueous ammonia 'and' amines. Irisof advantage therefore, to incorporate themin alkaline cleansing agents made up from saltshaving an alkalin'e reaction such as alkali carbonates, alkalisilicates,alkali borates and alkali polyphosphates-or incleansingiagents which. contain. such salts as Well as; possibly, capillarieactive wetting and cleansing agents and neutral salts: which are used for the treatment-of. scoured copper and alloys thereof with base metals. The content of cor-r'osion protective agents'according'tothe present invention depends to a great extent-on thespecific activity of'the Z-guanidino-aryloimidazole compound used, on the alkalinity of the treatment liquor, and onthe tempera ture and duration ofthe treatment. Generally amounts of up to 1% calculated on the non-aqueous" componen of such cleansing.v compositions are sufficient but also considerably less or more can be incorporated',-for'example 0.05 to 5%. I

The following examples illustrate the invention vtiitli out limiting it in any way. Wherenototherwi'se state parts are given as parts by weight and the'temperatui's are in degrees centigrade.

Example] An aqueous solution containing 4.0 g. tech. tetrasodium pyrophosphate 1.0 g.. 2.4-di-tert. amylphenol polyglycol ether perilitre attacks brasspiate and nickelsilver plate-while forming strong oxidation tints; in addition som'eof themetal dissolves. At a temperature of to over'a' period of 24 hours, the loss in weight of' elementary metal is Brass 7.0 g] sq..'m./ 24 hours." Nickel silver 14.6 g./ sq; m'.'/24 hours.

If 3 mg. of Z-guanidi'nobenzimida'zole"is added for ever litre of the above treatment liquor and a parallelte' is "made then, under the same conditions, there are "the" following losses in weight:

the secured shining appearance of "themntreateclpl'ati'n is retained.

Example 2 Brass plate and nickel silver plate are treated with 8 g. of the following composition of washing agents in a tiitre of tap water:

3.0 parts of tetrasodium pyrophosphate,

1.0 part of the sodium salt of ethylendiamine tetraacetic acid,

2.0 parts of soap (sodium salt of stearic acid),

0.5 part-of the sodium salt of a secondary alkyl sulphate :(Shells Teepol) Example 3 Qwashing is done in a scoured copper vessel with a composition of washing agents made vup as follows:

10. parts of a usual marketed pentasodium triphosphate, 15.,parts of tetrasodium pyrophosphate,

5 parts of sodium silicate (waterglass),

l5.parts of sodium carbonate,

5 parts of alkylaryl sulphonate (consisting chiefly of dodecyl benzene sulphonate),

15 parts of fatty alcohol sulphate (laurel-sulphuric acid ester),

115 parts ,of carboxymethyl cellulose,

0.2 part of an optical brightening agent of the 1.4-bisr,triazinylaminostilbene-2.2'-disulphonic acid class, 33-.3parts of. sodium sulphate cryst.

After washing 30 times at 80-90 for 30 minutes each time, the loss in weight of the vessel was 0.50 g. elementary copper for each square metre. In a parallel trial the composition of washing agents was implemented by the addition of 0.05 part (calculated on the solid substances) of Z-guanidinobenzir'nidazole and the same procedure was followed. In this case, the loss of metal was only 0.06 g. for each square metre. In addition the surface of the copper remained completely scoured.

The other 2-guauidinobenzimidazole compounds listed in Example 2 can be used in this test with the same result.

Example 4 0n contact with scoured copper of a washing liquor containing 8 g. per litre of a compositlon of washing agents made up from 6 parts of sodium carbonate, 2 parts of higher fatty acids, 01 part of carboxymethyl cellulose, 018 part of sodium perborate,

a strongly coloured oxide layer is formed on the metal even at room temperature and particularly at higher temperatures. If, however, a few milligrammes per litre of one of the inhibitors listed below is added to this washing liquor, then the copper remains completely scoured:

*Z-guanidinobenzimidazole, 6-chloro 2 guanidinobenzimidazole, 6-methyl-Z-guanidinobenzimidazole, G-ethyl- 2-guanidinobenzimidazole, 6-nitro-2-guanidinobenzimidazole, 6-acetylamino-Lguanidinobenzimidazole, 6-methoxy-Z-guanidinobenzimidazole, 6-ethoxy 2 guanidinobenzimidazole, 6 -methyl sulphonyl-Z-guanidinobenzimidazole, 6-ethyl sulphonyl-Z-guanidinobenzimidazole, 6-

butyl sulphonyl-Z-guanidinobenzimidazole, Z-guanidino 4.5: 1'.2'- naphthimidazole, 2 guanidino 5'- ch1oro-4.5 1'.2'-naphthimidazole.

What I claim is:

1. A process of preventing the corrosion of coppery metal surfaces by alkaline aqueous solutions, which com prises bringing said coppery metal surfaces into contact with alkaline aqueous solutions containing from 1 to parts per million of a corrosion inhibitor of the formula wherein Ar represents a member selected from the group consisting of o-phenylene and o-naphthylene radicals which contain no water-solubilizing groups which dissociate acid in neutral water.

2. A process of preventing the corrosion of coppery metal surfaces by alkaline aqueous solutions of a watersoluble cleansing agent normally tending in aqueous solution to cause corrosion of coppery metal, which comprises bringing said coppery metal surfaces into contact with alkaline'aqueous solutions of a water-soluble cleansing agent containing from 1 to 100 parts per million of a corrosion inhibitor of the formula wherein Ar represents a member selected from the group" consisting of o-phenylene and o-naph'thylene radicals which contain no water-solubilizing groups which dissociate acid in neutral water.

3. A process of preventing the corrosion of coppery metal surfaces by alkaline aqueous solutions of a water soluble cleansing agent containing a surface-active agent and alkali metal phosphates, which comprises bringing said coppery metal surfaces into contact with alkaline aqueous solutions of a water-soluble cleansing agent containing a surface-active agent, alkali metal phosphates and from 1 to 100 parts per million of a corrosion inhibitor of the formula wherein Ar represents a member selected from the group consisting of o-phenylene and o-naphthylene radicals which contain no water-solubilizing groups which disrosion inhibitor is 6-methyI-Z-guanidino-benzamidazole. 8. A process according to claim 1, in which the corrosion inhibitor is 6-chloro-2-guanidino-benzimidazole.

9. A corrosion preventing composition consisting of a water-soluble cleansing agent dissolving in water with an alkaline reaction, the aqueous solutions of which tend to cause corrosion of coppery metal on contact, and of 0.05 to 1%, calculated on the dry weight of said cleansing agent, of a corrosion inhibitor of the formula wherein Ar represents a member selected from the group consisting of o-phenylene and o-naphthylene radicals which contain no water-solubilizing groups which dissociate acid inneutral water.

10. A corrosion preventing composition consisting of a water-soluble cleansing agent, which comprises a surface-active agent and alkali metal phosphates and which dissolves in water with an alkaline reaction, the aqueous solutions of which tend to cause corrosion of coppery metal on contact, and of 0.05 to 1%, calculated on the dry weight of said cleansing agent, of a corrosion inhibitor of the formula wherein Ar represents a member selected from the group consisting of o-phenylene and o-naphthylene radicals which contain no water-solubilizing groups which dissociate acid in neutral water.

11. A corrosion preventing composition according to claim 9, wherein the corrosion inhibitor is Z-guanidinobenzimidazole.

12. A corrosion preventing composition according to claim 9, wherein the corrosion inhibitor is 6-nitro-2- guanidino-benzimidazole.

13. A corrosion preventing composition according to claim 9, wherein the corrosion inhibitor is 6-methoxy-2- guanidino-benzimidazole.

14. A corrosion preventing composition according to claim 9, wherein the corrosion inhibitor is 6-methyl-2- guanidino-benzimidazole.

15. A corrosion preventing composition according to claim 9, wherein the corrosion inhibitor is 6-chloro-2- guanidino-benzimidazole.

References Cited in the file of this patent UNITED STATES PATENTS 2,618,603 Schaefier Nov. 18, 1952. 2,618,606 Schaeffer Nov. 18, 1952 2,706,179 Tundermann Apr. 12, 1955 

1.
 2. A PROCESS OF PREVENTING THE CORROSION OF COPPERY METAL SURFACES BY ALKALINE AQUEOUS SOLUTIONS OF A WATER SOLUBLAE CLEANSING AGENT NORMALLY TENDING IN AQUEOUS SOLUBLE TO CAUSE CORROSION OF COPPER METAL, WHICH COMPRISES BRINGING SAID COPPERY METAL SURFACES INTO CONTACT WITH ALKALINE AQUEOUS SOLUTIONS OF A WATER-SOLUBLE CLEANSING AGENT CONTAINING FROM 1 TO 100 PARTS PER MILLION OF A CORROSION INHIBITOR OF THE FORMULA 